Remove Sisimai::Message->load method and other related codes

[azumakuniyuki]

• The followings will be removed at Sisimai 5.1.1
  • Sisimai::Message->load
  • https://github.com/sisimai/p5-sisimai/blob/5-stable/lib/Sisimai/Message.pm#L102-L142
  • Code for calling Sisimai::Message->load
  • https://github.com/sisimai/p5-sisimai/blob/5-stable/lib/Sisimai/Message.pm#L39-L47
  • https://github.com/sisimai/p5-sisimai/blob/5-stable/lib/Sisimai/Message.pm#L429-L436
  • Other related codes in t/040-message.t and t/500-fact.t
• Does anyone call Sisimai::Message->load?
  • Does anyone specify load or order parameter at the argument of Sisimai::Message->rise() method or Sisimai->rise() method?